Variable-Reluctance Sensor Interface with Differential Input and Adaptive Peak Threshold

 

Part Number	Replacement	Explanation

Description

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The MAX9924–MAX9927 variable reluctance (VR or magnetic coil) sensor interface devices are ideal for position and speed sensing for automotive crankshafts, camshafts, transmission shafts, etc. These devices integrate a precision amplifier and comparator with selectable adaptive peak threshold and zero-crossing circuit blocks that generate robust output pulses even in the presence of substantial system noise or extremely weak VR signals.

The MAX9926/MAX9927 are dual versions of the MAX9924/MAX9925, respectively. The MAX9924/MAX9926 combine matched resistors with a CMOS input precision operational amplifier to give high CMRR over a wide range of input frequencies and temperatures. The MAX9924/MAX9926 differential amplifiers provide a fixed gain of 1V/V. The MAX9925/MAX9927 make all three terminals of the internal operational amplifier available, allowing greater flexibility for gain. The MAX9926 also provides a direction output that is useful for quadrature-connected VR sensors that are used in certain high-performance engines. These devices interface with both new-generation differential VR sensors as well as legacy single-ended VR sensors.

The MAX9924/MAX9925 are available in the 10-pin µMAX^® package, while the MAX9926/MAX9927 are available in the 16-pin QSOP package. All devices are specified over the -40°C to +125°C automotive temperature range.

MAX9924, MAX9925, MAX9926, MAX9927: Simplified Block Diagram Enlarge+

Key Features

• Differential Input Stage Provides Enhanced Noise Immunity
• Precision Amplifier and Comparator Allows Small-Signal Detection
• User-Enabled Internal Adaptive Peak Threshold or Flexible External Threshold
• Zero-Crossing Detection Provides Accurate Phase Information

Applications/Uses

• Camshaft VRS Interfaces
• Crankshaft VRS Interfaces
• Vehicle Speed VRS Interfaces